Abstract
A newly-developed mobile yarder altered from a power shovel was applied to thinning in a steep sugi (Cryptomeria japonica D. DON) stand. The physiological load of workers was investigated and it was found that the RMR estimated by heart rates was 0.4 for operating the yarder, 9.6 for loading, 8.0 for delimbing (in forest land) and 6.8 for bucking (on forest road) . Using the simulation based on these values of the RMR, we estimated the relationships between the width of cutting blocks and the energy consumption of workers. The result was that the energy consumption including setting up and dismantling of the yarder was minimum when the width was 62.2 m for the operator of the yarder, 41.2 m for a choker setter, 36.6 m for an unhooker and 41.6 m for a delimbing man. We also calculated the energy consumption of the workers for 8 hours and found that it was 1120 kcal for the operator of the yarder, 2588 kcal for a choker setter, 2606 kcal for an unhooker and 2929 kcal for a delimbing man. Compared with the energy consumption of an operator, that of the other workers was found to be far higher.
